1. Field of the Invention
This invention relates generally to firefighting equipment and infrared signage devices, and more particularly to a portable emergency exit marking device which includes electrical heating elements in the form of letters forming infrared exit wording that is visible by a thermal imaging camera, an audible alarm, and a blinking light for guiding firefighters to the exit of a burning smoke-filled building.
2. Background Art
Firefighters and other emergency personnel operating inside a smoke-filled or burning building or other structure often become disorientated or lost due to the heat and severely limited visibility in the dense smoke and darkness, and many lives are lost each year because they become trapped by the structure are otherwise unable to escape due to operating on a limited air supply because they are unable to find an exit from the burning structure.
Various attempts at overcoming this problem include positioning a fire fighter at an exit of a burning building with a flashlight, or placing a flashlight or lantern at the exit, with the beam of the lamp pointing in the direction from which the firefighter expects to exit later. However, the intensity of light generated by a flashlights and lanterns typically cannot effectively penetrate heavy smoke or flame. There are also currently available, audible and visual alarms, such as strobe lights and LED's, reflectors, colored objects, and similar safety devices that are used to mark an exit. These types of device are also typically not effective due to the limited visibility inside the burning building is limited because of the heavy smoke or flame.
Merendini et al, U.S. Pat. No. 5,825,280 discloses a portable safety light and audible signal apparatus for placement in proximity to a building exit, to guide one or more fire fighters and emergency personnel to the exit during conditions of intense smoke and heat. The portable safety light and audible signal apparatus has a housing for containing, an audible signal generator capable of generating at least three distinctive audible signals, a strobe light mounted upon the top portion of the housing; an inverted U-shaped handle mounted on opposing sides of the strobe light, at least one switch in electrical communication with the strobe light and the audible signal generator, and a portable power supply located within the housing, in electrical communication with the switch.
Popps et al, U.S. Pat. No. 6,864,799 discloses an emergency lighting device for firefighters that marks a viable exit for a building which includes an audible sounder and a number of laser diodes in a housing with lenses that create panes or sheets of light. For example, there may be four laser diodes oriented at various angles. The housing of the device can have prongs that allow the device to pierce drywall so as to mount it near a door or window, as well as an adhesive or cement for mounting the housing on other vertical surfaces. The housing also has a tapered wedge shape and can wedge a door in an open position.
Carolan, U.S. Pat. No. 7,196,614 discloses a guidance device for aiding rescue personnel to quickly locate potential fire victims in a building which includes a body having multiple reflective fields, and a mounting member for securely mounting it to a surface. The body's reflective surfaces may be oriented to reflect approaching light from the top, bottom, left, and right, thereby enhancing its visibility regardless of an approach mode of rescue personnel, and regardless of an orientation in which the guidance device is mounted. The guidance device may include an element such as a metal disc capable of absorbing heat to enhance the guidance device's detection by a thermal imaging camera, or be configured to cause emission of light from responsive to detection of light (e.g. from a firefighter's flashlight). One or more guidance devices may be sold as part of a kit that includes an identification marker mountable adjacent an entry door of a building, and instructions for coordinating mounting positions of the identification marker and the guidance device relative to their respective doors.
Although these prior are exit indicating devices may be effective for their intended purposes, the existing exit indicating devices do not lend themselves to effectively identify the exit in dense smoke and darkness or flame.
More recently, high-tech devices have been developed to improve the safety of fire fighting personnel, such as for example, thermal imaging cameras (TIC's) carried by the firefighters, global positioning units, and head mounted displays in communication with a computer.
Smoke has a large component of micron-sized carbon soot particles in it which absorb visible-light wavelengths. Thermal imaging cameras (TIC's) penetrate heavy smoke and overcome the handicap of darkness to visualize heat sources in situations of limited visibility. Typically, the firefighter relies on thermal patterns visible in the camera display that indicate the presence of a person, a hot spot which may be the source of the fire, or some other thermal characteristic or heat emitting object. Although thermal imaging cameras (TIC's) significantly increase the visibility and display thermal patterns that indicate the presence of a person, hot spots, heat emitting objects, and thermal characteristics of the environment inside the burning structure, they to not identify the exit of the burning structure, nor do they identify conventional exit markers that rely on visible light because the visible wavelengths are outside of the infrared band of the electromagnetic spectrum.
Antonio II, et al, U.S. Pat. No. 7,626,506 discloses a thermal signature device that enables a firefighter to be located with a thermal imaging camera. The device includes an infrared LED which emits light in the infrared wavelength frequency. The infrared LED is situated in a housing that may be temporarily fastened to a firefighter's clothing and manually actuated by the firefighter with a pushbutton to emit infrared signals that may be identified by an infrared camera. The thermal signature device may include a receiver in data communication with the emitting-element such that the emitter may be actuated by a remote transmitter. The housing may include a permanent fastener such as adhesive such that the firefighter may selectively attach the housing to a stationary object, such as a wall, where it may be more visible or to another person in distress. A location determining system utilizing the thermal signature device provides an infrared camera for detecting the emitter-element.
Seibert et al, U.S. Pat. No. 7,659,527 discloses infrared marking device and method for marking an object, such as a door, inside a structure, such as a smoke-filled or burning structure. The infrared marking device comprises a ring-shaped, elasticized outer sleeve having a tubular sidewall and an amount of a self-heating exothermic chemical material confined inside the tubular sidewall of the outer sleeve. The self-heating exothermic chemical material emits infrared radiation when activated. The infrared radiation is visible in a thermal imaging camera. The method comprises activating a self-heating material confined inside a marking device to initiate an exothermic reaction that emits infrared radiation and applying the marking device to an object inside the structure.
These types of devices that utilize infrared LED's and exothermic chemical heaters attached to a firefighter's clothing or to a stationary object, such as a wall, typically only show up in the imaging system as a point or a “hot spot” and are difficult to distinguish from other hot spots, heat emitting objects, and burning objects in the environment of the burning structure.
Various object identifiers have also been developed in the filed of firearms that utilize infrared light for use in producing night vision targets and in targeting and sight calibration for firearms equipped with infrared sighting scopes and thermal imaging cameras.
Scott U.S. Pat. No. 4,524,386 discloses a thermal target display system and method which generates thermal or infrared radiation patterns simulating the thermal “signature” of “real-scene” objects such as vehicles, buildings or personnel which the nightvision or thermal imaging sights were designed to detect, rather than utilizing the real-scene objects themselves as targets. The system utilizes a plurality of individually controlled, active heat-radiating thermal elements disposed in an array to form a thermal screen or target. The thermal elements are disposed upon a substrate of a thermally and electrically insulating material and each element is composed of a layer of film of a conductive resistive coating deposited on substrate between two conducting bus bars across which a differential voltage is impressed to heat the resistive coating. The thermal screen is interfaced with a video system and is energized in response to a video image representing the real-scene object in the infrared spectrum. The gray scale representations of the individual video image pixels are converted into signals which define desired temperature differentials of each of the individual radiating elements of the thermal screen or target, these signals controlling the energization of the thermal elements so that the thermal screen generates a radiation pattern which corresponds to a particular video frame. The thermal radiation pattern, representative of the thermal signature of the real-scene object, can be enhanced and manipulated through conventional video processing techniques.
Boyer, U.S. Pat. No. 7,528,397 discloses a method of creating signage system visible by infrared cameras and infrared weapon sights for calibration of infrared weapon sights. In one embodiment, the signage system comprises a laminar target or sign member formed of a “no power” or “reverse power” material, such as a painted Mylar film, with a front and back surface. The front surface has the characteristic of interfacing properly with any materials adhered to it. The back surface has the characteristic of having low emissivity. A “zeroing target” is printed on the back surface. When viewed through an infrared imaging device, the target will be readily apparent. The laminar member allows any conceivable sign, target, etc. to be created using traditional printing means, such as a silk screening. For additional clarity in the thermal weapons sight, the laminar member can be completely or partially warmed, such that in the area where warmth is applied, the difference in infrared energy emitted from the non-printed front surface relative to the printed surface will increase, and as this difference increases, the clarity in the thermal weapons sight will increase. In a preferred embodiment, the heat is applied to the front surface of the laminar member by a heat generator and a heated surface, which may provide thermal dissipation and/or mechanical stability and may comprise a single object or multiple objects. In a preferred embodiment, a commercially available biodegradable chemical heater is used which begins to warm when exposed to oxygen in the air and requires the target or just the heater to be packaged in an air-tight package to prevent the heater from operating before use. In another embodiment, the heat is applied utilizing an electric heater. Boyer teaches that the heater shape does not have to assume a specific shape because the infrared image is created on the front surface and is a function of the printing, not the geometry of the heater; and that various signs, targets, etc. can be created by altering the shape of the insulator or the cutout portion of the insulator.
Although the prior art devices that utilize infrared light for use in producing night vision targets and in targeting and sight calibration for firearms may be effective for their intended purposes, they would not be suitable for use in a burning structure and would not be effective to indicate or identify an exit of the burning structure.